The petty voice inside our heads

What is it about human nature that prompts us to want to dismantle, pick apart, and destroy.  To get preverse joy in tearing down other people. What is it that when dismissed or discounted, forces us to increase our destructive drive.  This small petty voice of a child that surfaces again and again leading to dismissal, anger, hate, intolerance and war.  If only we could quiet it and work from a stance of love rather than hurt.